Automatic Signing Out

Bakers2

I have just had to retype a comment for the forum;  having composed one and hit the post button only to find it wasn't there and I'd been signed out
.  I am not a slow 'typer' and had been reading the conversations for awhile so had probably been signed in for quite sometime.  What I find infuriating
(this is not the first time it has happened) is that I do not know how long it is before you are automatically signed out - does anyone else know??